Machine presses of the aforementioned type are available in the state of the art, in various embodiments. For example (see EP 231735 A1), machine presses are already known in which the hydraulic drive system has two piston/cylinder units, by means of which the upper tool support is moved, and a single motor/pump unit (hydraulic assembly) that jointly supplies the two piston/cylinder units with hydraulic fluid. In this connection, application of fluid to the two piston/cylinder units is controlled by way of valves that can be activated by the machine control.
Furthermore, machine presses having two piston/cylinder units that jointly serve for movement of the upper tool support are known, in which the hydraulic drive system furthermore has two separate motor/pump units, which each supply only one assigned piston/cylinder unit with hydraulic fluid. The speed of raising and lowering the upper tool support is typically dependent on the motor speed of rotation, whereby a. switch between raising and lowering takes place by means of a reversal of the direction of rotation of the pump (reversing pump).
Another machine press having two cylinder/piston units, each supplied by a separate motor/pump unit and jointly serving for movement of the movement of the upper tool support, is known from EP 692327 A1. In the interests of improved efficiency, here an additional pressure storage system is provided. This system comprises two additional pump/motor units, each assigned to a motor/pump unit, which can be mechanically coupled with these, and a pressure storage unit. In phases of low power demand of the cylinder/piston units, the pressure storage unit is merely charged by means of the motor/pump unit operated in pump mode, whereas in phases of great power demand of the cylinder/piston units, i.e. at peak load, the motor/pump units—with fluid applied from the pressure storage unit—are operated in motor mode, in order to support the primary motor/pump units in this way.